Process of preparing glyoxal



Patented June 17, 1941 en 'STATES PATENT fiQ'FElC-E 2.24 349 PROCESS OF PREPARINGGLYOXAL I Heim'ich Lange, Frankfort n-theamaiiirnochst,

.Germany, assignor, by mesne assignments, to General 'Aniline '& Film Corporation, New York,- "N;"Y., acorporatio'n of Delaware I *oiDrawing. xApplication May27, 1939, Serial-No. 276,227., TIn'Germany June. 8, 1938 :The present. invention relates to a -process of preparingl glyoxal.

It is known that glyoxal can be made, invits monomericzform; only 'withdifiiculty-"and with' an insufiicient yield. "Ihez polymeric form. is. more easily accessible; but-most of the: known processes of its manufacture: lead to awproduct intermixed, more or less, witheinorganiccandiiorganic substances the. presence-of: which-impedes or even hinders further working; up. .The Zproductcannot the .:.purified' by distillationgsince the? polymericiglyoxal :cann'otfibe distilled and 'whenfsubjected' to :high temperatures is depolymerized only to a small extenttthergreaterpartwf it being condensedrto'formiresine-like products.

'.Now I have :"found sth'at' solutions 0f ilglyoxal havingra rhigh: degree. of purityzimay be: obtained by first transforming?rgiyoxaltetracetate, sin .a suitable'mannerginto thetcorresponding:glyoxaltetracetal,then?saponifyingithe=acetali'formed, in the presence :of water,3 bynneans'nf a comparativelyhstrcngi acid jicfor instance? a'di'lutesmineral acid; and :esterifyingI-itheracetic acid setirfree and distilling it. The residue of distillation after neutralizingithe mineral 'acid by me'ans of caustic soda solution; :contains only zwater' and glyoxal besides some trac'es of a mineral 'salt such as Na2SO4.

glyoxal tetracetate with-at 'least 4 "molsoi' an aliphatic; ;monoalcoholsand at ileast 4 mols of Water-Lin the presence of an -1 acid stronger -than acetic acid. The very smooth transformation of the tetracetate intothe-acetal is especially surprising.

If the transformation of the glyoxal-tetracetate into, the tetracetal and. .the 'saponification of; the acetal to .form thelglyoxal iscarried out in. one single reaction, in the presence-of the theoretical amount of .water and a moreor less large excess of an alcohol, for' instance an aliphatic monoalcohol such as methanol, ethanol .or propane]; theacetic 'acid is nearly quantitatively converted into the corresponding "ester, the. glyoxal being. obtained, in.a very pure state, in theIaq-ueous. solution; .theiyield corresponds with 90 to.96 perQcentof the theoretical. .Only traces .of alkalilsaltsofthemineral acids are. still contained iinI-the. solution. IThe excess .of-. alcohol usedlin the reaction may. amount to two to ten times the quantity theoretically.necessary which is .4,mols, calculated. upon 1-v mol ofglyoxal-tetrac- I etat'e. 'llhe water '.,is. preferably .used in -the theoretically; necessary. amount (likewise 4: mols This reaction may be represented by zthe following equation:

The process is carried out by heating 1 mol of up'tothe'dou'blethereof. V I As-acids 1 theremay, for: instance, be 1 used the following; sulfuric acid, hydrochloric 'acidyphoshoric ,acid, benzenesul onic acid, .oxalic. acid,

corresponding. tofll .mol of glyoxal-tetracetate) tartaricacid orthelike.

-'I'he acids are used ina quantity as it-is'usual for acatalystin saponifica'tionand acetalization processes. Theimore -acid is added the more rapidly proceedss-the reaction. e e

The reaction may already be carried out at temperatures of about 30 0., but it is suitable to heat the mixture to boiling.

The reaction is complete when no longer an ester is formed.

The following examples serve to illustrate the invention, but they are not intended to limit it thereto; the parts are by weight, the ratio of parts by weight to parts by volume is that of the kilo to the liter:

(1) 262 parts of glyoxal-tetracetate and 2.5 parts by volume of concentrated sulfuric acid are heated to boiling in the presence of 1000 parts by volume of alcohol and 50 parts of water. The whole is distilled, on the steam bath, in the course of 7 hours, until no alcohol or ethyl acetate any longer distils. The residue of distillation is diluted with half its volume of water and then again distilled under the same conditions. Whereas the combined distillate (1150 parts by volume) contains, besides some water, nearly the theoretical amount of the excess of alcohol and the ethyl acetate, the residue of distillation (168 parts by volume) contains pure glyoxal amounting to a yield of 92 to 96 per cent. The glyoxal solution, which is feebly' acid with mineral acid and is, for instance, of 28 per cent strength, may directly be used for further reactions. In case a higher concentration is desired or if the acid reaction is inconvenient, the solution may either be concentrated by evaporating to '70 per cent strength or it may be neutralized by means of a solution of barium hydroxide or sodium hydroxide.

If a larger quantity of sulfuric acid is used, for instance five times the above named quantity, the reaction proceeds more rapidly.

(2) The procedure is the same as indicated in Example 1 with the exception that the reaction mixture is, after the first distillation on the steam bath, not diluted with water and again distilled, but the residue obtained by the first distillation is immediately subjected for a short time to steamdistillation in order to blow off the residual alcohol and ethyl acetate.

Per cent of the theoretical Yield of glyo Yield of ethyl acetate 99 (3) The procedure is the same as that indicated in Example 1 with the exception that, instead of sulfuric acid, there is used the equimolecular amount of oxalic acid, namely 4.13

parts.

Yield of glyoxal: 94 per cent of the theoretical.

(4) 262 parts of glyoxal-tetracetate are treated, according to Example 1, with 2.5 parts by volume of concentrated sulfuric acid in the presence of 192 partsof alcohol (theoretical amount) and 50 parts of water. There are obtained 270 parts of a distillation residue containing 20.8 per cent of glyoxal which corresponds with 56 parts of glyoxal. The yield of glyoxal amounts, therefore, to 96 per cent of the theoretical. The ethyl acetate is, in this case, obtained in the distillate only in an amount corresponding with 86 per cent of the theoretical yield.

(5) 262 parts of glyoxal-tetracetate and 2.5 parts by volume of concentrated sulfuric acid are heated to boiling, for 12 hours, under reflux in the presence of 500 parts by volume of methanol and 50 parts of water, and the reaction mixture is further treated as indicated in Example 1.

There are obtained 223 parts of a distillation residue containing 23.3 percent of glyoxal; the

.quired amount) and 25 parts by volume of water.

Yield of glyoxal: 93 per cent of the theoretical.

lclaimz' 1. In the process of preparing glyoxal the step which comprises heating 1 mol of glyoxal-tetracetate with at least 4 mols of an aliphatic monohydroxy alcohol and at least 4 mols of water' in the presence of a non-oxidizing acid stronger than acetic acid.

2. In the process of preparing glyoxal the step which comprises heating 1 mol of glyoxal-tetracetate with more than 4 mols of an aliphatic monohydroxy alcohol and 4 mols of water in the presence of a non-oxidizing acid stronger than acetic acid.

3. In the process of preparing glyoxal the step which comprises heating 1 mol of glyoxal-tetracetate with at least 4 mols of ethanol and at least 4 mols of water in the presence of a nonoxidizing acid stronger than acetic acid.

4. In the process of preparing glyoxal the step which comprises boiling a mixture of 1 mol of glyoxal-tetracetate with at least 4 mols of an aliphatic monohydroxy alcohol and at least 4 mols of water in the presence of a non-oxidizing acid stronger than acetic acid.

5. In the process of preparing glyoxal the step which comprises boiling a mixture of 1 mol of glyoxal-tetracetate with at least 4 mols of ethanol and at least 4 mols of water in the presence of a non-oxidizing acid stronger than acetic acid.

6. In the process of preparing glyoxal the step which comprises boiling a mixture of 1 mol of glyoxal-tetracetate with at least 4 mols of ethanol and at least 4 mols of water in the presence of sulfuric acid. 1

'7. In the process of preparing glyoxal the step which comprises boiling a mixture of 1 mol of glyoxal-tetracetate with at least 4 mols of ethanol and at least 4 mols of water in the presence of oxalic acid.

8. In the process of preparing glyoxal the step which comprises boiling a mixture of 1 mol of glyoxal-tetracetate with at least 4 mols of methanol and at least 4 mols of water in the presence HEINRICH LANGE. 

